In the formation of color paper it is known that the base paper has applied thereto a layer of polymer, typically polyethylene. This layer serves to provide waterproofing to the paper, as well as providing a smooth surface on which the photosensitive layers are formed. While the polyethylene does provide waterproofness to the paper, the melt extruded polyethylene layer on the backside of color paper has very little dimensional strength and cannot be removed. It has little utility other than to provide a balance package for curl and provide a degree of waterproofness. In conventional photographic products there is an overcoat which is primarily gelatin on top of the photosensitive layers. The overcoat provides a level of protection to help minimize scratches. It typically is a gelatin based material but also may contain other synthetic polymers, but needs to be water permeable to allow the processing chemistries to get into the photosensitive layers. Since it is water permeable, it offers little or no protection to the final image against spills or damage from liquids. Even small drops of water spilt on the surface of a photograph can ruin the image and value of the print.
It has been proposed in U.S. Pat. No. 5,244,861 to utilize biaxially oriented polypropylene in receiver sheets for thermal dye transfer. In U.S. Pat. No. 5,244,861 high strength biaxially oriented sheets are laminated to cellulose paper with low density polyethylene. These layers provide functionality to the imaging material, but they do not protect the image which is on top of the top side sheet.
In current photographic papers, the backside polymer layer is attached for the life of the print. Polyethylene is placed on each side of the paper to prevent processing chemical from wetting the paper base which would require long drying times for photoprocessing. Photographic paper is generally viewed and handled by the consumer and either displayed or stored in albums. Problems sometimes occur with fingerprints and scratches on the image side or even spills of liquids on the image surface which can render the print unusable or displeasing. Other types of protection other than the protection from physical damage would include the need to shield the image dyes and pigments from UV light which can cause dyes to fade or even cracking with long-term exposure. Also a method of protecting the image from atmospheric gases such as oxygen, nitrous oxide, and other harmful gases that may ruin the image would be helpful.